After @pwn20wnd team has dropped Unc0ver jailbreak for iOS 12.4, Apple quickly releases iOS 12.4.1 update to get rid of the jailbreak. In case you have already updated to iOS 12.4.1 version, but you want the jailbreak, you should quickly downgrade your iPhone/iPad to iOS 12.4 version before Apple stops signing it.
Apple is likely to stop signing iOS 12.4 in the next few days, so you should right now consider returning to the lower version on your iPhone/iPad. This is even applicable for A12.x Bionic devices like iPhone XS, XS Max since an iOS 12.4 jailbreak for them seems to be released soon.
How to downgrade to iOS 12.4 on iPhone/iPad for jailbreak
This process might be risker but you can downgrade to lower iOS version without losing data on your iPhone/iPad. It will be faster than the second method, which includes both erasing your device and reinstall the iOS version.
Steps to downgrade iOS 12.4 without losing data
Here is how to downgrade to iOS 12.4 without affecting any data on your iPhone/iPad
Step 1: On your device, go to Settings > tap on Apple ID banner at the top and disable Find My iPhone
Step 2: Download the iOS 12.4 firmware file for your iPhone/iPad from https://ipsw.me/.
Step 3: Unlock your iOS device and connect it to the computer.
Step 4: Open iTunes software and click on your iOS device icon from the top left corner.
Step 5: Click on the Summary tab in the left sidebar.
Step 6: Hold the Option key on Mac or Shift Key in Windows and select Check for Update option.
Step 7: Browse to the folder containing the iOS 12.4 ipsw firmware you downloaded earlier.
Step 8: You will be prompted to update your iOS device to iOS 12.4 and iTunes will verify the update.
Step 9: Click on Update and your iOS device will downgrade to iOS 12.4 version
This method is much safer, but it will need more time since it will erase your iPhone storage. Make sure you have already created an iOS 12.4 backup of data since you are unable to restore an iOS 12.4.1 backup on your iPhone/iPad after the downgrade. If you don’t have a previous backup, you cannot restore your iPhone after returning to iOS 12.4 version.
Restore iOS 12.4 firmware on iPhone/iPad
Step 1: Downgrade iOS 12.4 firmware for your iPhone/iPad from https://ipsw.me/
Note: If you use Safari browser to download the firmware, make sure to disable the auto unzip feature. You can also add the .zip file and .ipsw file still works fine.
Step 2: Put your iPhone/iPad into DFU mode. You can read on this post to do so
Step 3: Connect your iPhone/iPad to the computer and power it off by holding the Power button. Hold it for 3 seconds
Step 4: Hold the Home button ( Volume buttons on newer models) while still keeping the power button for 10 seconds.
Step 5: Release the Power button while still holding the Home ( Volume buttons) until there is a popup from iTunes, saying that it has detected your iPhone in Recovery mode.
Step 6: Hit the OK button.
Step 7: Hold the Option key on Mac or Shift key in Windows and select Restore iPhone (iPad) button. If you just press the Restore iPhone button without holding the Option or Shift key, iTunes will automatically restore the latest iOS version.
Step 8: Browse to the iOS 12.4 firmware you downloaded earlier.
Step 9: Click on Restore and Update button to proceed.
Step 10: iTunes will now verify the iOS 12.4 update and start installing it on your Android device. The process could take 10 minutes
Once the restoration to iOS 12.4 is done, your device will automatically boot up the ‘Hello’ screen. Simply follow the on-screen instructions to complete the setup wizard, and then restore your iPhone/iPad from an available backup.
That’s how to downgrade your iPhone/iPad back to iOS 12.4 version. If you have any question, let’s know in the comment below.